If her parents are old-fashioned and your significant other wouldn't find it offensive or sexist, you could consider asking her parents for permission. Although asking a father's permission is considered by many to be old-fashioned, it hasn't died out precisely because it's a gesture that suggests that you respect her and her family and that you're always going to be considerate of her family. It's also a sign of politeness, and what family can resist that? But again, it really depends on the girl and her